Data on fender transformers?

[tomrasdf]

Quick question:

What's the amperage rating on the 6v tap of a SF 50 watt bassman?
I'd like to know before I try el34s in a d-clone.

Also:
I've scoured the interweb trying to find some sort of database with this sort of info on fender transformers with not much luck. Does such a thing exist?

Thanks much.

[benoit]

Where did you get the transformer?

[Fischerman]

Lots of folks have run EL34s in Bassman/Bandmasters without failures. My first 'build' was an old basket case non-reverb BF Bandmaster that I made into a Marshall with EL34s (in the late 90's) and it still works fine...I gigged with that amp for a couple of years. I would suggest playing the amp for a while with 6L6s and then check the heat of the PT as well as the heater voltages. Then let it cool down, put the EL34s in it and rebias, and repeat. If the voltage doesn't drop too much and the PT doesn't get too hot you're probably good.

[tomrasdf]

Where did you get the transformer?

The transformer came with the amp. It was someone else's project amp that I rescued from ebay (serious mess).

Lots of folks have run EL34s in Bassman/Bandmasters without failures.

Thanks for comfirmation. I'd gathered this was the case, but I'm still looking for solid numbers I could back it up with.

[rhinson]

typically those trannies will have a 4A rated winding but it's probably a conservative rating. with the el34's taking 3A of that you should be able to run 4 12ax7's without any problem i would think. and the tip above about measuring the voltage under load is a good way to tell if it's stressed or not--an old tried and true method. rh

[tomrasdf]

Cool. Thanks much for the guidance!
-TR

[CaseyJones]

The way to be sure is to measure your filament voltage under full load. Ideally you want to see 6.3 volts. If it drops below say 6 volts you're pushing it.

For reference EL34s use almost double the filament current of 6L6s at 1.5 amp. 12AX7s use .3 amp each, it doens't sound like much until you add them up.